The early modern period was not an era of great technical innovations. Even into the 18th century, people were still mainly trying to improve on the great inventions of the Middle Ages. The spectrum of available energy sources was limited: Wood remained indispensable as a building material and the most important fuel, and machines could only be moved by muscle, water or wind power. The salt works technology in Halle had also hardly changed over the centuries, and the Pfännerschaft extracted its salt as it had always done. With the introduction of hard coal in the state-owned boiling smelters around 1700, however, a new era dawned.

Medieval conditions

Towards the end of the 17th century, the Thalsaline still extracted its salt almost as in the Middle Ages. The earliest illustrated description of it comes from Georg Agricola's (1494-1555) famous mining manual De re metallica. The precise explanations and woodcuts suggest that the Saxon physician and polymath probably knew Halle's saltworks from his own experience.

Salt extraction in a saltworks in Agricola's book

Salt workers and boiling tools in: Georg Agricola: De re metallica libri XII […], Basileae 1556, 448. Basel, Universitätsbibliothek: hv I 22, https://doi.org/10.3931/e-rara-52830, Public Domain Mark

More than 100 years after Agricola, the Halle salt count Friedrich Hondorff (1628-1694) wrote the first standard work on salt production in Halle: Das Saltz=Werck zu Halle in Sachsen befindlich. In it, he describes in detail the ownership structure, legal system and work processes at the Thalsaline. Today, Hondorff's work gives us valuable insights into local boiling technology and salt production in the 17th century.

In 1749/50, the Halle jurist and Salt Count Johann Christoph von Dreyhaupt (1699-1768) published a two-volume Beschreibung des Saal-Creyses: a lavishly illustrated treatise on the history and culture of the city of Halle and the surrounding area. To this he added Hondorff's outdated writing on the Thalsaline as an appendix and supplemented what had changed since 1670. Today both editions of Hondorff's work are important sources for the history and technology of salt production in pre-industrial Halle.

Wodd, straw and clay – the salt huts

The salt was produced in the salt huts. These were simple half-timbered houses made of fir or spruce wood, straw and clay. Each hut had a large dug-in barrel, half of which stood in the alley and half in the house. So the brine could be poured in from the outside and taken out from the inside.

Houses of special construction, all smoked and in many places eaten away by the sharp salt, frequent moss on the roofs and everywhere a black soil coloured by cinders.

About the Thalsaline at the end of the 18th centuryTopographie Pittoresque [...], 1798

The heart of each hut was the boiling room. Here stood the boiling hearth, above which hung a pan made of sheet iron on a wooden frame. At the pan, the salt worker and his servants performed the strenuous, sweat-inducing work of boiling salt.

When the salt was ready, it had to dry for some time before being sold. To do this, it was carried to the salt place, a raised area at the back of the hut. There were also storage areas for straw and firewood.

They all wear straw hats on their heads and aprons because of the heat in the hut, but are otherwise naked.

Georg Agricola on the workers in the boiling huts in the mid-16th century

From exampel to model

The model of a large salt hut from around 1700 is one of the few historical testimonies that can still give us a vivid impression of the old boiling huts on the Thalsaline. It was probably made as a teaching model for visual instrution in the orphanage schools. It was used to illustrate the typical construction of the salt huts and the traditional salt boiling process. The model is mentioned for the first time in the catalogue of the Cabinet of Artefacts and Natural Curiosities, which was newly established in 1741 and where it is still exhibited today.

The year of construction and builder of the model are not yet known. The still preserved equipment corresponds to a simple, wood-fired boiling hut of the 16th and 17th centuries. However, the remains of a pump in the brine barrel indicate that the model could have been built in 1699 at the earliest, when such pumps became common.

Die big model aof a salt hut – virtual

Explore the virtual 3D model of the large salt boiling hut and follow the animated process of salt boiling.

Salt extraction takes place in two phases: First, the brine must be heated, boiled down and purified. This is called »Stören«. Only during the subsequent »Soggen« process do salt crystals form in the concentrated brine. For coarse-grained salt, the brine should have a temperature of about 70° C during this process. One work of salt – two filled baskets weighing about 100 kg together – requires 36 buckets of brine and four hours of time.

  1. Two carriers pour brine from a vat, which they carry on their shoulders by means of a pole, from the outside into the brine barrel at the boiling hut.

  2. In the boiling hut, a servant heats the hearth with logs. Then he pours 22 buckets of brine into the boiling pan on the hearth.

  3. The boiling process itself is now the responsibility of the boiling master, who is called the »Salzwirker« in Halle. He is assisted by his servants.

  4. The hut gradually fills with smoke and steam. Flames are shooting up the wall behind the pan.

  5. To purify it, the salt boiler stirs some cattle blood into the brine. This produces foam, which he skims off. The servant then pours another 14 buckets of brine into the pan and adds wood to the hearth.

  6. After some time, the brine swells up and the salt boiler adds some beer. The alcohol in it promotes the formation of salt crystals, which already form small islands on the brine. Now the brine must no longer boil.

  7. The salt crystals combine and sink to the bottom of the pan as coarse-grained salt. With the help of a so-called crutch, the boiler carefully pulls it to the edge of the pan. He now fills the dripping wet salt with a wooden shovel into two wicker baskets, which the servant has previously placed in a rack above the pan. The salt is layered and whipped up over the edge of the basket until the typical shape of the salt pieces is formed. Meanwhile, the excess brine drips back into the pan.

  8. The servant takes the filled baskets out of the rack and places them next to the hearth. Later he carries them upstairs to the salt place, where the still damp pieces of salt have to dry for some time. Later they can be sold to traders.

  9. After one work of salt has been boiled, a new work is started.

Is the detailed model possibly a replica of a very specific salt boiling hut? The house sign painted on the facade – a duck – at least suggests so, because a boiling hut called »Duckbird« actually existed. It is marked on the plan of the Thalsaline from 1746, in the middle of today's place called »Hallmarkt«. Even its ground plan and the location of the brine barrel match the model.

Among the changing owners of the »Duckbird« in the 18th century is the Kraut family, a family of Pfänners. Two of their sons, Christian Friedrich (1650–1714) and Johann Andreas (1661–1723), were influential Prussian civil servants in Berlin. They were in contact with August Hermann Francke and promoted his orphanage project. A connection between the Kraut family and the model is therefore probable.

Ground plan of the Thalsaline from 1746

[Translate to English:] »Grundriss des Thals zu Halle samt dessen Graentzen, Saltz-Brunnen und Saltz-Kothen. 1746«, copper engraving in: Johann Christoph von Dreyhaupt: Pagus Neletici Et Nudcizi [...]. Theil 1, Bd. 2, Tab. AA. Halle, Francke Foundations: AFSt/B Sb 0056

From wood to hard coal

Like iron smelting and glass production, salt boiling also consumed vast quantities of firewood, which seemed to be becoming increasingly scarce. Therefore, resourceful minds were already trying to reduce consumption at the end of the 16th century by means of new boiling techniques. In Halle, too, tinkerers and »project makers« experimented with wood-saving boiling hearths and alternative fuels, which was expensive but led nowhere. For fear of financial losses, many Pfänners later distrusted any promises of innovation and preferred to stick to the tried and tested method.

Climate fluctuations, harsh winters with frozen rivers and local deforestation repeatedly led to shortages. Halle also had to deal with wood shortages from time to time and worried about its energy supply due to rising demand and prices. Whether the forests were already too heavily deforested at that time or whether it was rather poor logistics that caused the shortage is still disputed in research, however.

The salt works in Saulnot near Mömpelgard in Württemberg (today Montbéliard, France) was one of the pioneers in the field of salt boiling technology. As early as 1593, Heinrich Schickhardt (1558–1635), a master builder at the court, had developed boiling furnaces of a high technical standard, with air ducts and flues for operation with hard coal. It was not until 100 years later that this technology also found its way into Halle.

New Technology

The Brandenburg Elector wanted to have high-quality salt produced in his boiling huts on a large scale, but as cheaply as possible. The cheap fuel was to be hard coal from his own mines in Wettin and Löbejün northwest of Halle, which could also be transported upstream on the Saale river to Halle. But the coal burned badly in the conventional boiling cookers and the smoke made the salt black and bitter. So the boiling technology had to be renewed from the ground up.

They did not even shy away from industrial espionage: The government of Electorate Brandenburg sent a spy to the Allendorf salt works in Hesse, which had already been heating its ladles with hard coal in the 16th century. Details scouted out there were incorporated into the boiling experiments in Halle.

After many attempts, the boiling master Johann Bötticher (1639–1713) finally achieved a breakthrough in 1693. His solution was similar to Schickhardt's construction in the Saulnot salt works: a hearth with an iron coal grate, ash fall and controlled air supply, a brick chimney for the flue gases and a fume outlet above the pan. The latter led the boiling steam out into the open via a roof outlet.

Bötticher's real invention, however, was the heat pipes on the drying floor of the boiling hut, heated by the waste heat from the boiling fire. This way the salt dried faster than ever.

The salt is then taken to a yard, where it is roasted by the heat of iron pipes and sold immediately. It certainly makes these huts warm enough.

Albrecht von Haller (1708–1777)Travel diary, 1726

With the new method, Bötticher succeeded in boiling impeccable salt that could rival that from Lüneburg. As a reward, he was appointed chief boiling master of the royal salt production.

By 1701, all of the sovereign's boiling huts had been modernised in Bötticher's style. Not so with the Pfänners. Only a few were open to the new process and modernised their technology. It was not until the middle of the 18th century that all the Pfännerschaft's boiling huts were heated with hard coal.

Soot particles between the grains of salt were virtually a trademark of the Hall salt. With the new method, however, the salt became cleaner. After the Pfännerschaft switched to hard coal, they had soot added to their salt for some time to dispel doubts about its origin.

Bötticher's technology in the model

The small teaching model of a salt hut from the Cabinet of Artefacts and Natural Curiosities of the Francke Foundations features all of Bötticher's innovations in a simple form. It thus corresponds to the current state of boiling technology of the time and represents the important experimental phase of Prussian salt production. It was made by the Halle pastor, educator and inventor Christoph Semler (1669–1740). In 1708 he opened a Mathematical and Mechanical School in Halle for prospective apprentices of the craft – the first »Realschule«, a school for visual instruction, in Germany. There, a teacher taught technical correlations primarily using models that Semler made especially for this purpose.

In the Cabinet of Artefacts and Natural Curiosities there are other fascinating models from Semler's workshop, for example a brewery house and a lathe with miniature tools. Semler left them to his colleague August Hermann Francke in 1718, who was pursuing a similar school project, but it was never realised. Together with other teaching aids, the models initially belonged to the »Mechanical Chamber«, later they became part of the art and natural collection in the former orphan boys' dormitory.

The small salt hut model in the first »Realschule«

Already on the cover, the accompanying booklet to Semler's "Real-Schule" advertises the models and topics covered in class.

The teaching material on the salt boiling hut not only explained its most important components on the model, but also conveyed solid basic knowledge about the salt boiling craft on the Thalsaline.

The small model – virtual

Explore the virtual 3D model of the little salt boiling hut.

In the past, the royal cesspits were also located in the city, where the extra brine was boiled, but now they have been relocated outside the city to the Saale, where the brine is also conducted through pipes.

Johann Georg Brieger (1764–?)Historisch-topographische Beschreibung der Stadt Halle im Magdeburgischen, 1788, S. 18

The electoral boiling huts on the Thalsaline stand at the beginning of the Prussian salt industry around 1700. The technology developed there created the basis for the state-owned salt works in Halle and Schönebeck. For some time, the local royal saltworks were the largest salt producers in Prussia, until they were overtaken by the Schönebeck saltworks in the 1730s.

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